How To Use Epsom Salt for Plants and Gardens

Epsom salt has long been a fail-safe soother for humans. But could it also be a great garden tool?

Inexpensive and soothing, Epsom salt has long been a home remedy staple around the world. Sore, swollen feet? Soak them in Epsom salt. Can’t sleep? Take a bath with Epsom salt. Constipated? You guessed it! Epsom salt is Food and Drug Administration (FDA) approved to get things moving again.

And it turns out your garden plants may benefit from Epsom salt as much as you can. Read on to learn how.

What Is Epsom Salt?

Epsom salt (AKA magnesium sulfate) isn’t salt at all. Rather, it’s a compound composed of magnesium, sulfur and oxygen. It was reportedly named after the town in England where it was discovered.

For hundreds of years, people claimed it relieved a multitude of symptoms and conditions. However, scientific evidence has not specifically borne out its efficacy.

Does Epsom Salt Benefit Plants?

According to the Epsom Salt Council (yes, there is such a thing!), the National Gardening Association has found roses and pepper plants grew larger and bushier and bore more fruit or flowers when treated with Epsom salt. Some experts still contend the evidence is anecdotal. But there are few drawbacks to using Epsom salt in the garden, and the benefits could be fairly bountiful.

Erinn Witz, garden expert and co-founder of Seeds and Spades, says magnesium and sulfur are vital to a plant’s ability to convert sunlight into food. They also help the roots absorb other key nutrients from the soil.

Jeremy Yamaguchi, CEO of Lawn Love, says Epsom salt is “phenomenal” for plant growth. “If you look at commercial growth-boosting mineral mixtures — not naming any names here — they contain mostly the same ingredients as Epsom salt, along with a few other things that have tertiary benefits, but aren’t as necessary,” he says.

What Plants Are Epsom Salt Especially Good For?

According to Witz, nightshades such as tomatoes and peppers, as well as roses, seem to respond well to Epsom salt treatments. Clive Harris of DIY Garden says acid-loving plants like rhododendrons, camellias, blueberries and azaleas might also benefit.

If your plants are yellowing around the edges and between the veins, there’s a chance you have a magnesium deficiency going on. Epsom salt may be able to help.

Is Epsom Salt a Good Fertilizer?

According to Witz, magnesium and sulfur help young seedlings establish strong, healthy root systems. She says that when you start your tomatoes and peppers from seed, water newly planted seeds with a mixture of one tablespoon of Epsom salt to four cups of water. “This can aid in germination and give your baby plants a boost,” she says.

If you have lackluster houseplants, Witz says it’s possible they’ll benefit from minerals in Epsom salt, too. “Since indoor plants don’t have access to the normal mineral content of outdoor soil, it’s easy for them to be lacking in some nutrients,” Witz says. You can spray them, even directly on the leaves, to give them a boost.

Is Epsom Salt a Weed Killer?

Experts seem to agree: Epsom salt, even when combined with other ingredients, is not a weed killer. It operates much more like a fertilizer. And yet, some internet recipes claim the opposite. Regular salt can kill weeds, which is perhaps where the confusion began.

How Much Epsom Salt Do Plants Need?

Treating your garden with Epsom salt won’t require a bulk buy. A small amount goes a long way. And if your soil is rich in magnesium and sulfur already, it is possible you may not need it at all.

But soils that are deficient (this can be sorted out with a pH test) could really benefit, especially if you grow the plants that love a little extra magnesium. Even if you want to give your soil a boost before planting a whole garden, you still only need a small amount.

The Epsom Salt Council recommends the following:

  • Houseplants: Two tablespoons per gallon of water; feed plants monthly.
  • Roses: One tablespoon/foot of plant height per plant; apply every two weeks. Scratch one-half cup into soil at base to encourage flowering canes and healthy new basal cane growth. Add one tablespoon of Epsom Salt to each hole at planting time.It
  • Shrubs such as evergreens, azaleas and rhododendrons: One tablespoon/nine square feet. Apply over root zone every two to four weeks.
  • Garden startup: Sprinkle one cup/100 square feet. Mix into soil before planting.